However, this causes a reduction in the availability of carbondioxide (CO2) in the hens’ blood, a condition recognized as respiratory alkalosis. As egg shells are
composed mainly from calcium carbonate (CaCO3), this reduction in blood CO2 levels, consolidated with an increase in blood pH and a subsequent decrease in Ca ions utilized by the shell gland, leads to thinner or softer shelled eggs (Arima etal.,1976).